The treatment of wastewater has many potential benefits, one example of which is to achieve an acceptable discharge for disposal or recycle. Processes for the treatment of wastewater include, for example, centrifugation, pressure filtration (e.g., microfiltration, ultrafiltration, nanofiltration, reverse osmosis), membrane distillation, electrolysis, chemical treatments, a combination thereof, etc. In the agricultural and food processing industries, it is known to treat wastewater using pressure filtration processes. Utilizing a combination of pressure filtration processes separates successively smaller particles from resulting permeates. Generally, microfiltration (MF) separates particles between about 0.1 microns and about 10 microns, ultrafiltration (UF) separates particles between about 0.1 to about 0.005 microns, nanofiltration (NF) separates particles between about 0.005 and about 0.001 microns, and reverse osmosis (RO) separates particles that are smaller than about 0.001 microns.
Pressure filtration processes and systems are described, for example, in U.S. Pat. No. 5,250,182, U.S. Patent Application Publication No. US 2005/0252858 and International Patent Application Publication No. WO 2005/123603, each of which is incorporated by reference in its entirety herein.
In a cellulosic ethanol process, including the distillation of ethanol and water fermentation broth, a whole stillage is produced. This whole stillage may be treated to yield a thin stillage. Applicant has recognized it would be desirable to treat whole stillage and/or thin stillage from a cellulosic ethanol process using unique treatment processes in order to separate constituent parts suitable for recycling or discharge. Applicant has also recognized that it would be desirable to treat wastewater from sources other than a cellulosic ethanol process using unique treatment processes to achieve beneficial results. In addition, Applicant has recognized that it would be desirable to operate treatment processes in modified batch mode, rather than in continuous mode, to yield greater water recovery.